Eric (EVLXX) made several different maps with his sniffer, and had more than a few of them dyno tested. I know that with his fuel mileage map, which I assume is the same one that zero has, I can get over 50 mpg running two-up with just a slight hesitation on acceleration. When you live out in the forsaken wilderness, 25 more miles out of a tank can make a world of difference.
If you run with a pack of XX's at less than stupid speeds for very long, the stench of unburnt gas is enough to make your clothes stink